Reading Reaction Journal #5

Porous carbon nanofibre arrays can be made using crab shells as a template

From crab shell to fuel cell

09 April 2010
Crab shells provide a cheap and convenient template to make high performance carbon electrodes for energy storage and conversion, say Chinese scientists.
Carbon materials have many potential applications, including as electrodes in supercapacitors and fuel cells. The pore structure is known to affect their physicochemical properties and is normally controlled by using a porous hard template such as zeolite or silica. But the process usually involves using hydrofluoric acid to remove the templates, which can be complex and costly.
A research group from Fudan University, led by Yong-Yao Xia, has demonstrated that crab shell has a well aligned porous structure at the microscopic level. Exploiting this unique structure, they have generated porous carbon nanofibre arrays by combining the hard crab shell template with an established soft templating method. 'Biological templates are generally abundant, renewable, inexpensive and environmentally benign compared to artificial templates,' explains Xia.
After burning the crab shell in air, the porous template mainly consists of calcium carbonate. Adding a soft copolymer template and resol precursor forms the carbon framework. Heating under nitrogen gas removes the soft template and the hard template can be dissolved in hydrochloric acid.
'The crab shell hard template is not only easy to remove but also hierarchically porous,' says Rui Zhang, an expert in porous carbon materials at the Shanghai Institute of Technology. The templated carbon nanofibre arrays retain this hierarchical porosity, forming pores of three sizes. The largest result from the packing of nanofibres, the medium pores from voids between the nanofibres and the carbon nanofibres themselves contain the smallest pores.
The pore structure is suitable for charge storage by ion adsorption/desorption as an electrode material for supercapacitors or platinum/palladium catalyst loading for fuel cell applications, says Xia. Aided by the large surface area and complex structure, Xia' material shows excellent results in both cases.
Xia's team is now using crab shell to template other porous materials as well as investigating alternative shellfish templates.






References
Wise, E. (2010, April 09). From crab shell to fuel cell. Chemistry World, Retrieved May 03, 2010, from http://www.rsc.org/Publishing/ChemTech/Volume/2010/05/from_crab_shell.asp

Vocabulary
Template: a shape made of metal, plastic, or paper which is used to make copies or to guide someone in cutting something
Fuel: a substance such as oil or gas that is used to provide heat or power, usually by being burned
Aligned: to put (two or more things) into a straight line
Hydrofluoric acid: an acid containing hydrogen and chlorine
Copolymer: a polymer consisting of two or more different monomers, polymer: a chemical substance consisting of large molecules made from many smaller and simpler molecules
Precursor: something which happened or existed before another thing, especially if it either developed into it or had an influence on it
Nitrogen: a gas with no colour or taste which forms about 78% of the Earth's atmosphere and is a part of all things which live
Adsorption: The process by which molecules of a substance, such as a gas or a liquid, collect on the surface of another substance, such as a solid. The molecules are attracted to the surface but do not enter the solid's minute spaces as in absorption. Some drinking water filters consist of carbon cartridges that adsorb contaminants.
Platinum: a valuable metal that is silver in color, does not react easily with other elements, and is used in jewelry and in industry
Ion: an atom that has a positive or negative electrical charge as the result of adding or taking away an electron
Nanofibre: A kind of fibre, but it is so small that you cannot see with your eyes

Summary
Chinese scientists have found a way, which uses crab shells to supply a cheap and easy template, to make high performance carbon electrodes for save and switch. Carbon materials have many important submissions. However, if the process requires the use of hydrofluoric acid to remove the templates, it is very expensive and hard. Because the pore structure will affect their physicochemical properties, they will look for another method to complete this research. Eventually, a research group from Fudan University, led by Yon Yaoxia, proved that crab shells have well aligned porous structure at the microscopic level. The crab shell is a kind of biological templates, so it is a renewable, inexpensive and environmentally material. After the crab shell burns in the air, the mainly thing is calcium carbonate. After special processing, it can be dissolved in hydrochloric acid. Rui Zhang says, “the crab shell hard template is not only easy to remove but also hierarchically porous.” The moldboard carbon will become pores of three sizes. Xia says: The pore structure is not only suitable for charge save by ion adsorption as electrode material for supercapcitors but also suitable for platinum catalyst loading for cell submissions. Now Xia’s team uses crab shells to template other porous materials.

Reaction
This article talks about scientists using biological materials to replace the materials, which is costly and difficult to achieve. Indeed, in the world, the resources have become less and less. Although the biological materials are renewable, if people overuse the materials from nature, it is also cannot renew. This article introduces how to get energy from crab shells for human beings and it also introduces how to use inexpensive and environmental materials to develop new energy. That is a benefit for human beings, but it is not good for the natural balance. Do the scientists think about whether will they overuse the crab shells, what will happen next? Right, we cannot see the crab. I have to say that crab shell being able to transform to a fuel cell is a miracle. It can change the resource configuration. Before we used a fuel cell from chemicals which wastes a lot of materials and cannot get the expected results, but now they use biological materials, which can release more energy than chemicals. At the end, I hope scientists can look for some materials without animals. Fortunately, the scientists are looking for other materials to replace the crab shells, for example, shellfish templates. However, I come out with the same question about new materials in my mind.